The invention relates to an apparatus at a spinning preparation machine, especially a flat card, roller card or the like, wherein a clothed, rapidly rotating roller is located opposite at least one component at a spacing, the spacing being influenced by the nature and/or number of components.
In calculating and setting carding gaps it is known to make use of a known arrangement of the machine in question and its components, with material-related and construction-related parameters of components and component groups also being used for calculations. If the configuration of such a machine is then changed in respect of the nature or number of the components in question, it may well be necessary to modify the calculation and setting of carding gaps accordingly. For correct carding gap calculations and adjustments, the parameters for different machine configurations have to be communicated to the control system of the machine. Manual input of those parameters by the machine operator is onerous and may be associated with errors.
In a flat card, the spacings between the cylinder clothing and the surfaces located opposite it (counterpart surfaces) are of major importance in terms of machine and fibre technology. The carding result, namely degree of cleaning, nep formation and fibre shortening, is substantially dependent on the carding gap, that is to say on the spacing between the cylinder clothing and the clothings of the revolving and fixed card flats. The guiding of air around the cylinder and the dissipation of heat are likewise dependent on the spacing between the cylinder clothing and clothed or non-clothed surfaces located opposite, for example take-off blades or casing elements. The spacings are subject to different influences which in some cases act in opposite directions. Wear on clothings located opposite one another results in widening of the carding gap, which is associated with an increase in the number of neps and with a decrease in fibre shortening. Increasing the speed of rotation of the cylinder, for example in order to increase the cleaning action, results in a widening-out of the cylinder and also of the clothing, on account of the centrifugal force, and therefore in a narrowing of the carding gap. Also, when processing large amounts of fibre and certain kinds of fibre, for example synthetic fibres, an increase in temperature causes the cylinder to expand to a greater extent than the rest of the machine surrounding it, so that the spacings are reduced for this reason also. The machine elements located radially opposite the cylinder, for example fixed carding segments and/or take-off blades, also expand.
The carding gap is influenced especially by the machine settings on the one hand and by the condition of the clothing on the other hand. In a flat card having a revolving card top, the most important carding gap is located in the main carding zone, that is to say between the cylinder and the revolving card top unit. At least one clothing, delimiting the work spacing of the entire carding zone, is in motion. In order to increase production by the flat card, it is desirable to select the operating speed of rotation—or operating velocity—of the mobile elements so that it is as high as fibre processing technology will allow. The work spacing is located in the radial direction (starting from the axis of rotation) of the cylinder.
In the case of carding, ever greater amounts of fibre material are being processed per unit time, which gives rise to higher speeds for the work elements and higher installed capacities. Increasing fibre material throughput (production) results in increased heat generation as a result of the mechanical work even when the working surface area remains constant. At the same time, however, the technological result of carding (sliver uniformity, degree of cleaning, nep reduction etc.) is being continually improved, which gives rise to an increase in active surfaces that are in carding engagement and to closer settings of those active surfaces relative to the cylinder (drum). The proportion of synthetic fibres processed (where more heat, compared to cotton, is generated by the contact with the active surfaces of the machine as a result of friction) is continually increasing. The work elements of high-performance flat cards are nowadays fully enclosed on all sides in order to meet the high safety standards, to prevent the emission of particles into the spinning room environment and to minimise the maintenance requirement of the machines. Gratings or even open material-guiding surfaces which allow air exchange belong to the past. As a result of the mentioned circumstances, the introduction of heat into the machine is markedly increased whereas the heat removed by convection is markedly reduced. The greater heating of high-performance flat cards that is caused thereby results in greater thermoelastic deformation which, because of the non-uniform distribution of the temperature field, affects the set spacings of the active surfaces. The spacings decrease between the cylinder and the card flats, doffers, fixed card flats and take-off positions provided with blades. In extreme cases, the gap set between the active surfaces can be completely consumed as a result of thermal expansion so that components in relative motion collide. The consequence, then, is major damage to the high-performance flat card concerned. All this means that, especially, the generation of heat in the working region of the flat card can result in disparate thermal expansion when the temperature differences between the components are too great.
In order to reduce or avoid the risk of collisions, the carding gap between clothings located opposite one another is, in practice, set relatively wide, that is to say a certain safety spacing is provided. However, a large carding gap results in undesirable nep formation in the carded sliver. Rather, an optimum value, especially a narrow value, is desirable, as a result of which the proportion of neps in the carded sliver is substantially reduced. Moving the elements located opposite one another towards one another results in a change in the spacing (carding gap) over the entire width of the machine.
The carding result is crucially influenced by the carding gap. This means that a carding gap which is, as far as possible, uniformly narrow over the working width leads to optimum results. From this it follows that, for the cylinder, the quality of its cylindrical shape is of crucial importance. In relation to the cylinder, a further problem lies in the fact that it is unevenly heated over the working width as a result of varying coverage by material and gap variations caused by manufacturing tolerances. In addition, the heat is dissipated to a greater extent in the edge regions than in the middle, leading to a build-up of heat there. This results in a temperature gradient from the middle of the working width to the edges. The disparate thermal expansion caused thereby gives rise to the cylinder becoming distended outwards in a convex shape (bulging) and accordingly leads to a deterioration of the carding gap. Consequently, the result of carding is adversely affected. Because the cylinder is the counterpart for all carding and take-off locations, this quality reduction occurs at all locations. The heating during operation gives rise, in the middle of the elements located opposite one another, for example the cylinder and carding elements, to a large amount of expansion, which decreases towards the edge regions. It is disadvantageous that, as a result thereof, the carding gap is uneven over the width of the flat card and, in the middle region, there is a risk of collision between the components.
In spinning preparation machines such as flat cards, fixed carding elements are much used. These fixed carding elements comprise a profiled carrier member and clothings attached thereto. The profiled carrier members can differ in terms of their construction and materials, the consequence of which is disparate dimensional stability and heat dissipation. From DE 38 11 681 A there is known a profiled carrier member for a fixed carding element, which can have different cross-sections. The profiled carrier member is made of an aluminium alloy. On replacement, the carding gap has to be matched to the new cross-sectional shape. This problem also occurs when a complete set (plurality) of card flats, each comprising a profiled carrier member and carding element, in the revolving card top unit of a flat card is replaced by a set having a different constructional arrangement and/or being made of a different material. Known profiled carrier member materials include cast iron, steel and plastics. In the afore-mentioned cases, determining and inputting the properties of the at least one new profiled carrier member for modification of the carding gap is labour-intensive.